AuthorTopic: Epson 7900 from the inside - out (Read 869783 times)

My most recent focus has been finding the proper chemical to dissolve dried HDR Ultrachrome Ink. We found that, but the deadly clogs persist. We can only reach a small percentage of the two ends of these clogs, but the meat of the clog is untouched. The next step in this direction is soaking longer, which I have decided against. I am changing tack. It's too dangerous I feel, soaking with RED too long. The reason for this is very simple. Each channel runs two inks. The most delicate link in the chain which keeps these two separate inks separate, is the bond of the printhead face to the piezoboard. Once this goes soft, green and orange won't be green and orange anymore, instead they'll both be brown. If your head hasn't died yet in the face of cleanings, this will kill it for sure.

These piezoboards are amazingly intricate. Even though I have a stereo microscope, and can see these boards in great detail, I have to admit they are elusive things to map your way around. They are very difficult to light under the scope, and depending on how you light them they can and do change their shape straight before you. This makes it very difficult to understand exactly what you are seeing. Then there is the fact that typically they are caked with dried ink. It's a challenge. But recently, after the successful cleanings with RED, I have got some clearer views of these things under the scope. Another discovery was viewing them while submerged in water. This cleared things up even more.

What I have confirmed now is that the line of 358 consecutive chamber walls are indeed built on one horizontal deck. I knew this before, but what I did not know is that the deck they are built on is actually transparent. The next thing I learned recently is that beneath these transparent chamber wall lined decks, there is a second open reservoir containing free flowing ink which runs UN-compartmentalized, for both the width and the length of the entire deck. Stick that in your hat and consider what's next..

Upon the very closest, submerged in water under halogen lights examination I have managed to perform to date, I have discovered that at one end of each piezo chamber, at the very bottom, directly downward from the placement of the nozzle opening in the printhead face, there are incredibly tiny "steps". Three total. I cannot confirm what they are at this point, but I am suspect that they might actually lead to the un-compartmentalized ink reservoir below. Why you ask do I think this, if we already know ink is supplied to the chambers by passing through the tiny space over the "speed bump"? I have no $U*O%&)#$-ing idea, yet, but I do have an unsolved mystery to share which may be related..*paragraph note: when I say "pressure" I am talking nearly immeasurable pressure. When you create negative pressure at the rear of the head in order to suck fluid up through the face of the head, you get resistance. When you apply positive pressure to the rear of the head in order to push fluid out the face of the head, you get resistance. Nothing happens. But after a while of soaking things do begin to move. It does become possible to both draw fluid up through the face of the head into the chambers and out the back, and to push fluid through the chambers and out the nozzle openings in the face. So here-in lies the mystery; how in the love of $*)%! can it become possible for both cleaning fluid, and ink mind you, to both exit and enter the chambers through the nozzle openings, if the chambers are still clogged so solid that they don't fire once back in the machine? It can't of course, which brings us farther down this rabbit hole..

I have been sheepishly dodging my shadows for the past week about the fact that in reality I do not know how these heads work. Not REALLY work anyway. I mean, I have seen plenty of diagrams of piezoelectric nozzles by now. But none of them look like what I see in these X900 heads. So what gives?

I now think there could be two ways ink flows through the last elements of these printheads. I also now think this is why we have the variety of cleanings that we do. What if ....and I realize this is a big "IF".... these flexing chamber walls don't flex at all? What if they're just walls? And what if there is more to these X900 piezo nozzles than simply a hole in the roof at the end of an ink-filled hallway? What if these "steps" are elements of an actual nozzle, supplied not by the ink in the chambers, but by the reservoir below? The successful firing of these nozzles could in some way relate, perhaps via pressure (negative or positive), to the ink inside these chamber walls?

Stay with me for a minute here..

If a pairs cleaning "sucks" ink from the face of the printhead without firing the nozzles, it's main purpose could be simply to draw ink through the chamber passages, cleaning them instead of the actual nozzles ("steps") themselves. It could be that power cleanings, the cleanings that actually fire the nozzles as well, are intended to clear the firing elements of the actual nozzles. Lastly, if heat plays a role in all of this, and we know that it does because anywhere you have movement you have friction, which is heat, added to which we have piezoelectricity which is also heat - then it could be that these chamber walls play a major role in cooling as well as the passage of ink. Let me say that this way, could it be that these chamber walls play a key role in cooling as well as the passage of ink? Could this by why ink has such a tendency to dry up between them, because they dissipate so much heat? ...Especially in power cleanings - which is why deadly clogs often get bigger after power cleanings?

I apologize for all the words. I don't understand this. I am trying to. Definitely I got ink to both enter, and exit the printhead face via pressure from the ink supply nipples in the back of the head. Yet the machine couldn't fire the nozzles. I know ink is intended to pass through those chambers as part of the firing process. How else would the ink help cooling, if it were not moving? That passage of ink through the chambers likely plays two roles. And ink exits our heads from two different routes.

EricWhat you have now shown us is how difficult it is to clear a head that is partially clean in the first place but not in what appears to be the vital working area of the head..And applying pressure through a syringe is not really usefull either as the liquid will flow no problem through the open reservoir area...and bypass the chamber area...Whatever coating Epson lined the chambers with does not seem to be doing its job

Yes that seems to be the case - forcing fluid through the head does nothing to clear dried ink in the chambers. And soaking them in aggressive fluids is wicked dangerous. Not sure what step to take next yet.

New person here, old clog in a 4900. Having read through all of this several times I remain amazed at your individual and collective persistance. Here's a question, and let me know if this is the wrong place to ask it. With one dead channel/color (in my case VLM), might it be possible to re-plumb the head and make use of the fact that there are two blacks, photo and matte? In my mind's eye this is really simple, just a matter of unplugging and replugging two tubes at one end of the other of them. Surely it's more complicated if not impossible. But for those of us that have but one bad color, is it possible to re-map the colors, then for example put a VLM cartridge into the unused black (say the Matte black if we are printing on glossy paper)?

New person here, old clog in a 4900. Having read through all of this several times I remain amazed at your individual and collective persistance. Here's a question, and let me know if this is the wrong place to ask it. With one dead channel/color (in my case VLM), might it be possible to re-plumb the head and make use of the fact that there are two blacks, photo and matte? In my mind's eye this is really simple, just a matter of unplugging and replugging two tubes at one end of the other of them. Surely it's more complicated if not impossible. But for those of us that have but one bad color, is it possible to re-map the colors, then for example put a VLM cartridge into the unused black (say the Matte black if we are printing on glossy paper)?

Even if you had the confidence to start tinkering with the hardware, I highly doubt this would work. You need to think of the whole process from the image file numbers onward in how the software and printer driver combine to deliver instructions about what drops to put where. If the reproduction of say VLM is needed, I suspect the instruction is being directed at delivering ink from the VLM channel, which is hard wired in firmware, not where you happen to place the VLM cartridge.

It's an interesting idea. Chasing the option of switching MK with PK at the head and not mentioning it to the machine - for instance if your PK was clogged and you didn't need PK, kind of works in my mind. Only problem is the hoses that connect at the head are not individual lines. They are a bank of nipples fixed in two rows on the head, and a bank of hoses fixed at the base of the damper unit. I can't imagine switching colors would be possible. You'd be better off buying an MK cleaning cart, filling it with PK ink, and charging the line with PK instead. Then just print using "MK". That would handle switching your inks. As far as actually printing on glossy paper while the machine thinks you have MK in the gun, I don't know.. Maybe profiles are different for more than just the blacks when printing on matte papers?

It's an interesting idea. Chasing the option of switching MK with PK at the head and not mentioning it to the machine - for instance if your PK was clogged and you didn't need PK, kind of works in my mind. Only problem is the hoses that connect at the head are not individual lines. They are a bank of nipples fixed in two rows on the head, and a bank of hoses fixed at the base of the damper unit. I can't imagine switching colors would be possible. You'd be better off buying an MK cleaning cart, filling it with PK ink, and charging the line with PK instead. Then just print using "MK". That would handle switching your inks. As far as actually printing on glossy paper while the machine thinks you have MK in the gun, I don't know.. Maybe profiles are different for more than just the blacks when printing on matte papers?

It also seems feasible that mk and pk are different enough to merit slightly different screening approaches to work with the other colors.

I have interesting news. Rather than continue with the guess work I decided to use my brain for a change. I smashed a channel to bits, strategically of course, and combed my way through the wreckage like a forensic scientist. I have confirmed the following:

1 - The chamber walls are not simply for cooling purposes. The power leads that fan out from the base connection at the channel source, rise up through the piezoboard and individually connect to each and every channel wall, separately. The electrical connection to each of the walls make contact at the base of each wall and run for the entire length of each wall.

2 - There are no "nozzles". At least not in the traditional sense. No nozzles in the chambers, no nozzles below the chambers. Not even any power supplied to that area, that I can find. These piezonozzles are a design I have not seen in any literature posted here, yet.

3 - There are (I believe) two ways for ink to enter a chamber - over the speed bump or up through the floor of the chamber directly under the nozzle opening. So, flushing fluid through with pressure can have no affect on the dried ink lodged in-between the chamber walls.

4 - if there were no secondary passages for ink to enter a chamber, then pairs cleanings (where the machine sucks ink from the face of the head) would either suck the dried ink out the nozzle opening, or if the dried ink didn't move at all they would probably end up sucking the floor of a chamber up through the nozzle opening. ....my current bet is the secondary opening in the floor under the nozzle is a one-way valve-type safety mechanism. That's the feel they give when you put pressure on them in either direction. No movement at first, then with more pressure suddenly they begin to flow. Repeat, same thing. Feels like a valve.

5 - there is a clear plastic membrane that seals the base of the piezoboards from the world (chamber) beneath them. Only way into a piezoboard, is through the ink fill port.

6 - there is NOTHING beneath a chamber but a wide open reservoir filled with ink, which runs the entire length and width of the entire chamber deck. Nothing below the "one way valve" into the chamber at all.

I am more confident than ever that those chamber walls are indeed our nozzles. Guess work, flushed..

ps - I have followed the electrical leads up through the chambers, into and through the piezoboards. All the honeycomb holes you see in pics I have posted - I don't know what they are or what they do, but they have no leads. Cooling is a decent guess.

It also seems feasible that mk and pk are different enough to merit slightly different screening approaches to work with the other colors.

Sal

I think Mark and Sal are close.....yes we can change pipes and chips relatively easily....but what i think will also be needing change are the algorithms to tell the printer to produce the same colours but with different pipes....or different colours with the same pipes...Its a recalibration of the printers profile really....oh for that cleaning solution.......

More fun facts for the evening's appetite. On the subject of ink cart shaking, which has come up quite a bit lately, I would like to add the ridiculously appropriate experience of a fellow racer on Luminous Landscape, my new friend Lee.

First off, this is how much Lee knows about what happens to ink left sitting in our carts too long:

In my book, that's a lot. Lee takes every cart he gets, apart. He drains the leftover ink from them and stores it all in clear plastic bottles, each color separate of course. So I talked to Lee about an experiment I did with an old cart I had hanging around. Told him I cut the plastic cart to shreds, gutted the insides, and cut my way into the foil bag that holds the ink. He interjected "You found not one trace of sediment did you.." I told him no I did not. Then he emailed me this picture taken in his basement. He said "Me either, and I've taken hundreds apart." Lee also told me in all the bottles full of ink that he has stored, the only color he's ever seen settle at all is yellow.

So anyone paranoid about their inks separating and settling in the carts, or their lines, or their dampers, like the muck you need to shake from the bottom of an Odwalla protein drink, I think it's safe to say rest easy. I don't know what Epson makes this ink out of, but that's impressive.

Eric - I hope you have the opportunity to tear apart a head from the 3880 which is relatively bullet proof compared to the pro Epsons. It would be interesting to see if there are any obvious design differences that can explain why my 3880 can go 3 years, with 3 year old ink, and never clog.

I've had a love affair with the 3880, but I'm another user ready to move to Canon for a 24-inch printer. Epson finally has serious competition in the wide boy category.

Sal, the 3880 is a Pro printer in the Epson line-up. It also qualifies for Epson Pro-Graphics service. There is a definite difference in ease of maintenance between this model (including its 3800 predecessor) and the x900s. There is some opinion that the lower nozzle count per sq. in. may be the explanation but in truth and in fact we don't know. There could be so many differences throughout the whole ink delivery system, from cartridge to paper.

As silly as it sounds (I know I thought it was crazy at first), unlock the wheels to the printer stand and gently roll the printer back and forth to agitate the ink cartridges. Switch sides and repeat. This avoids ruining the seals on the cartridges by repeated removal/insertion.

Direct my cart shaking post toward the person (can't remember who) who recently suggested a schedule of cart removal and agitation that was simply out of control. Anyone in that much of a panic over their inks settling, I hope this settles your soul. Obviously it's smart to agitate, but there is no need to jeopardize your machine over it. Remarkable stuff this ink is.

Next discovery revealed - we know what the honeycombs are for. In fact we know what all the pretty cut-out shapes that surround the flexing chamber wall sections of the piezo board are. It's called "mechanical adhesion". Any time you want to glue one thing to another it's best to prep one or both objects by roughing up their surface - to give the glue something to grab onto. Four minutes after it hit me straight in the forehead again, I took one of the removed printhead faces, flipped it over and examined it's underside. Yep. There are traces of clear glue residue all over the underside of the printhead's tin roof, and it's all in the many funky shapes of the piezoboard's honeycomb surface. Turns out these honeycomb shapes play a critical role in keeping the different inks in our channels from coming together inside the piezoboards.

All these discoveries are great. Learned a lot today. But still not what really matters...

So anyone paranoid about their inks separating and settling in the carts, or their lines, or their dampers, like the muck you need to shake from the bottom of an Odwalla protein drink, I think it's safe to say rest easy. I don't know what Epson makes this ink out of, but that's impressive.

ActuallyI am the culprit who is paranoid about agitation......guilty my Lord....

Bear with me please for going back over old ground but as we all know,the basic makup of ink is just 3 thingsPigment......to paint withResin......to stick your paint on to something like paperEmulsifier....to make the pigment and resin cooperate as they would normally like to go their separate ways...

And water of course is there in abundance too...NO AIR IS DESIREABLE UNTIL THE INK LEAVES THE NOZZLE..a printer in theory should behave no differently to an ink cartridge....

Agitation is the way that the emulsifier gets to bring the pigment and resin together...But its a subtle problem.....you should not of course expect to see sludge too often....nor would i expect to see anything in the innards of a dissected cartridge (which i have done several times too )simply because one has to agitate the cart to get it opened...Nor would i recommend pulling carts out to agitate...(i have constantly advised against doing this since i joined this thread..)..its so important .....you will wear down air seals and more importantly you stand a good chance of destroying the cartridge chip sensor in the printer which requires a technician to fix unless you are prepared literally to pull the machine apart yourself ... I had to do that twice...All that needs doing is GENTLY AND BRIEFLY rock the printer on its loosened wheels...maybe 1 second gentle touch ...in my case one printer had to be placed on a shelf so i made a simple timber base on wheels..put the printer on this base...simple stuff...Other printer manufacturers have automatic agitation programs built in to the printer and in my humble opinion its for no other reason than to give the emulsifier a chance to keep on top of pigment and resin components drifting apart....my next printer will not be agitated by me...it will have inbuilt agitation ...for sure..Mark and I have focussed on the servicing needs of 800 and 900I have been agitating in a programmed way for 75 days (with the previous 210 days as backup experience )with 5 auto checks at 15 day intervals ...4 of the autos were clear first time ...the bad one required 10 minutes time to clear.....no printing (2 a4s)...just stress testing..i never had that clog free pleasure in the previous 6 years of ownership of that printer....Mark achieved the same result on the 900 by printing 25 prints.....and he knows his printer intimitely...top class management and discipline.......in my case ,a few seconds daily has saved me piles of time and money on cleaning chores..Yes you are thinking that the 800 and 900 are completely different printers ..they cant be compared.....but didnt Epson tell you that the 900 would be smarter and clogs would virtually be consigned to the history books..

BUT BUTI may be wrong...and i need to know that i am wrong....

SO

TO DISPROVE my agitation theories and consequent paranoia ,i will now do a 75 day test with 5 autos AND NO GENTLE PRINTER AGITATION during this test period ....with zero printing of course...the only factors left in the equation this time will be TURN ON every day and epson k3 inks as usual....i should in theory come back with the same auto results (80% Autos clear first time or even 100% clear first time..) that would then indicate that autos without agitation is at least as efficient or more efficient than autos with agitation....Will let you know auto results after each 15 day interval so that the 75 days doesnt feel too long...